From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Mon, 29 Oct 2001 18:28:54 +0000 Subject: Re: [Linux-ia64] itc sync & clock_* Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Mon, 29 Oct 2001 10:10:44 -0800, Jesse Barnes said: Jesse> Regarding glibc though: we really don't want to have a Jesse> different version just for our systems, so I'd like to come Jesse> up with a generic solution. Oh, yes, I guess I wasn't quite clear in my response: the "ITC are synchronous" flag needs to be exported to user level (probably through a /proc file). glibc then reads that flag and if the ITCs are *not* synchronous, it has two choices: - if there is a driver for a fine-grained machine timer, it can use it - if no such driver exists, it will not be able to provide fine grained time stamps So, you'll have to define and implement a driver interface to your machine timer (on SN1 its in the chipset, right?). If you want to go ahead with this, you might want to take a look at the Intel multimedia timer spec as well. I have my issues with that spec (it doesn't provide sufficient alignment guarantees, in my opiniono), but considering it should help in designing an interface that will be useful not just for SGI machines, but for all "big" ia64 machines. Jesse> Maybe an ia64 specific clock driver that glibc could map in Jesse> to read synchronized clock info? Yup. The driver interface needs to allow direct user-level access to the fine grained timer. Though I'd say the interface should be able to accommodate hardware that can't map the timer into user space. --david